We don’t know where the Universe’s most energetic light and particles come from, therefore they remain a mystery.

Sure, we can track some, but the Universe is awash in gamma radiation and neutrinos that we can’t account for. A whole deal more. Astronomers have just discovered an explanation for some of them: black holes that are virtually inactive.

They claim that this explains the abundance of’soft’ gamma rays in the Universe without depending on cold (nonthermal) electrons, which has always been a problem explanation since electrons become thermalized on timeframes that are considered to be too short to create high-energy particles.

Neutrinos and gamma rays aren’t exactly uncommon. The most energetic type of light in the Universe, gamma radiation, has been discovered at extremely high energy — in the teraelectronvolt region.

Neutrinos, often known as ghost particles, are almost massless particles that float through space, hardly interacting with anything. We’ve found them at high energies as well.

The photons and particles within them require the existence of a cosmic accelerator to achieve these energy. High-energy objects, like as supernova remnants or a black hole actively eating matter, should be used.

Even after accounting for these high-energy sources, we’re left with an unsolvable gamma-ray excess in lower’soft’ energies, as well as a neutrino excess.

According to a group of researchers led by astronomer Shigeo Kimura of Tohoku University in Japan, the surplus might originate from an unexpected source: supermassive black holes that are almost but not quite quiescent – but not fully active either.

When a supermassive black hole is active, it is surrounded by an enormous disk of dust and gas that is progressively being sucked into it. The enormous forces at work in the space around the black hole heat the material in the disk, causing it to burn over a spectrum of electromagnetic wavelengths, including gamma radiation.

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Furthermore, some material is sucked around the black hole’s periphery along its magnetic field lines, which function as an accelerator, towards the poles, where it is propelled into space at a large fraction of the speed of light.

A supermassive black hole is considered to exist in the center of every galaxy, although not all of them are active. The supermassive black hole in our galaxy, for example, is a snoozer.

According to Kimura and his colleagues, the gamma-ray excess in the lower energy range – megaelectronvolts rather than giga- or teraelectronvolts – might be caused by supermassive black holes accreting at such a low rate that they are far less visible to our telescopes on Earth.

The group ran the numbers and found out how it would work. There is still some material whirling about these non-active black holes, and it gets heated up.

In reality, the temperature of this heated plasma may reach billions of degrees Celsius, high enough to produce gamma radiation in the megaelectronvolt range, or’soft’ gamma rays.

Protons may be accelerated to great speeds within this plasma. These high-energy protons may produce neutrinos when they interact with radiation and matter, which explains the neutrino excess. And there are enough of these silent supermassive black holes in the Universe to account for at least a fraction of the extra signals.

It’s only a theory at this point, but the math appears to be correct. Astronomers will have a better notion of what to look for in future observations now that they have this knowledge, and the riddle of those unexplained gamma rays will be closer to being solved.

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